3,657 research outputs found
A CROSS-CORRELATION TECHNIQUE FOR RELOCATION OF SEISMICITY IN THE WESTERN CORINTH RIFT
Local seismological networks provide data that allow the location of microearthquakes which otherwise would be dismissed due to low magnitudes and low signal-to-noise ratios of their seismic signals. The Corinth Rift Laboratory (CRL) network, installed in the western Corinth rift, has been providing digital waveform data since 2000. In this work, a semi-automatic picking technique has been applied which exploits the similarity between waveforms of events that have occurred in approximately the same area of an active fault. Similarity is measured by the crosscorrelation maxi-mum of full signals. Events with similar waveforms are grouped in multiplet clusters using the nearest-neighbour linkage algorithm. Manually located events act as masters, while automatically located events of each multiplet cluster act as slaves. By cross-correlating the P-wave or S-wave segments of a master event with the corresponding segments of each of its slave events, after appropriately aligning their offsets, the measured time-lag at the cross-correlation maximum can be subtracted from the arrival-time of the slave event. After the correction of the arrival-times, a double-difference technique is applied to the modified catalogue to further improve the locations of clusters and distinguish the active seismogenic structures in the tectonically complex Western Corinth rift
Holographic Renormalization of general dilaton-axion gravity
We consider a very general dilaton-axion system coupled to Einstein-Hilbert
gravity in arbitrary dimension and we carry out holographic renormalization for
any dimension up to and including five dimensions. This is achieved by
developing a new systematic algorithm for iteratively solving the radial
Hamilton-Jacobi equation in a derivative expansion. The boundary term derived
is valid not only for asymptotically AdS backgrounds, but also for more general
asymptotics, including non-conformal branes and Improved Holographic QCD. In
the second half of the paper, we apply the general result to Improved
Holographic QCD with arbitrary dilaton potential. In particular, we derive the
generalized Fefferman-Graham asymptotic expansions and provide a proof of the
holographic Ward identities.Comment: 42 pages. v2: two references added. Version published in JHEP. v3:
fixed minor typos in eqs. (1.6), (2.3), (3.20), (A.3), (B.8), (B.12) and
(B.22
Anatomy of bubbling solutions
We present a comprehensive analysis of holography for the bubbling solutions
of Lin-Lunin-Maldacena. These solutions are uniquely determined by a coloring
of a 2-plane, which was argued to correspond to the phase space of free
fermions. We show that in general this phase space distribution does not
determine fully the 1/2 BPS state of N=4 SYM that the gravitational solution is
dual to, but it does determine it enough so that vevs of all single trace 1/2
BPS operators in that state are uniquely determined to leading order in the
large N limit. These are precisely the vevs encoded in the asymptotics of the
LLM solutions. We extract these vevs for operators up to dimension 4 using
holographic renormalization and KK holography and show exact agreement with the
field theory expressions.Comment: 67 pages, 6 figures; v2: typos corrected, refs added; v3: expanded
explanations, more typos correcte
Gauge fields, ripples and wrinkles in graphene layers
We analyze elastic deformations of graphene sheets which lead to effective
gauge fields acting on the charge carriers. Corrugations in the substrate
induce stresses, which, in turn, can give rise to mechanical instabilities and
the formation of wrinkles. Similar effects may take place in suspended graphene
samples under tension.Comment: contribution to the special issue of Solid State Communications on
graphen
Determining the Solution Space of Vertex-Cover by Interactions and Backbones
To solve the combinatorial optimization problems especially the minimal
Vertex-cover problem with high efficiency, is a significant task in theoretical
computer science and many other subjects. Aiming at detecting the solution
space of Vertex-cover, a new structure named interaction between nodes is
defined and discovered for random graph, which results in the emergence of the
frustration and long-range correlation phenomenon. Based on the backbones and
interactions with a node adding process, we propose an Interaction and Backbone
Evolution Algorithm to achieve the reduced solution graph, which has a direct
correspondence to the solution space of Vertex-cover. By this algorithm, the
whole solution space can be obtained strictly when there is no leaf-removal
core on the graph and the odd cycles of unfrozen nodes bring great obstacles to
its efficiency. Besides, this algorithm possesses favorable exactness and has
good performance on random instances even with high average degrees. The
interaction with the algorithm provides a new viewpoint to solve Vertex-cover,
which will have a wide range of applications to different types of graphs,
better usage of which can lower the computational complexity for solving
Vertex-cover
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